I have a Stevens 512. It's okay but nothing special. I would not have bought it though... the story is that I did buy a new 612 SxS from gunbroker for $400 (and no shipping). I waited a year to find such a deal! Well, that gun shot okay but the stock was actually a little short for me so I had to add a recoil pad which was a little annoying.
Then, it started doubling - so I had a full auto SxS. I shipped it back to Savage and they sent me back a new 512 (silver receiver and all, it really was an upgrade). The 612 is discontinued, could not be fixed (aluminum receiver had issues it seems), etc, so they sent me a 512.
I am having to put on a rib riser on it as the gun shoots low and that annoys me. It fits great though, but I just put a 1/4" x 14" x [1/4" tappering down to 1/16"] square dowl on the rib just in front of the middle bead. When sighting along that, it shoots perfectly.
The ONE thing I hate about it is that it doesn't stay open all of the way. The extractors are still stiff or something so the action has a tendency to sort of close up a bit making getting to the under barrel a chore. If it didn't do that, the gun would be fine.
I am afraid to ship it back to Savage... I don't know what I'd get back. I wanted to have a little, lively 20ga SxS but have a slightly heavier O/U now. So odd.
The 512 is balanced a lot better than the 612, btw.